Equalizer for hydraulic brakes



Aug. 14, 1934. H. C. BOWEN 1,969,872

EQUALI ZER FOR HYDRAULIC BRAKES Filed July 20. 1928 2 Sheets-Sheet l Aug. 14, 1934. H. c. BOWEN EQUALIZER FOR HYDRAULIC BRAKES 2 Sheets- Sheet 2 Filed July 20, 1928 WN QN Patented Aug. 14, 1934 UNITED; STATES PATENT OFFICE Hydraulic Brake Company, Detroit, corporation of California Mich, a

Application July 20, 1928, Serial No. 294,262

7 Claims. (01. 188-152) This invention relates to a brake mechanism, and more particularly to an apparatus for correlating the pressures in several pressure systems used in connection with the brake mechanism of a motor vehicle. In many cases it is desirable to use a separate pressure system for the front and rear wheel brakes of a motor vehicle.

An object of the invention is to provide an apparatus in which the proper relative pressures may be maintained in different pressure systems.

A further object of the invention is to provide a'brake mechanism in which a plurality of pressure systems may be operated from a common operating means to effect different pressure results in the different pressure systems.

A further object of the invention is to provide an apparatus for preventing excessive pressures from being produced in any of the pressure systems used in connection with a brake mechanism.

A further object of the invention is to provide an apparatus for obtaining the proper sequence of operation of the front and rear wheel brake mechanisms.

Other objects and advantages will appear as the description proceeds.

A complete understanding of the invention may be had by reference to the following description taken in conjunction with the accompanying drawings, in which Fig. 1 is a schematic representation embodying the invention showing a separatepressure device for the front and rear wheel brakes;

Fig. 2 is a fragmentary side elevation of the apparatus embodying the invention; I

Fig. 3 is a plan view of the apparatus shown I in Fig. 2; and 4 Fig. 4 is a longitudinal sectional view of a link mechanism through which the pressure devices are actuated. K

Referring to the drawings, and more particularly to Fig. 1, a fluid pressure operated system is illustrated in connection with a hydraulic brake system for a motor vehicle in which the front wheel brakes 6 and the rear wheel brakes '7 are actuated by separate pressure devices 8 and 9 respectively. The pressure device 8. comprises a piston 11, which may be .reciprocated in the cylinder 12 to produce a pressure in the fluid system by means of a lever 13. The pressure device 9 similarly consists of a piston 14, which may be reciprocated in the cylinder 15 to produce a fluid pressure by means of a lever 16. The levers 13 and 16 are connected through links 18 and 19 respectively to a common manually operated pedal 17.

Each of, the links 18 and 19comprises a bifurcated rod 21, which is attached at its bifurcated end to the pedal 17, and the other end, which is threaded, is adapted to be inserted in an aperture 22 of a clevis 23. Surrounding the threaded rod 21 is a sleeve 24, which is slidably mounted thereon and is provided at one end with a flange 25. A

spring 26 is interposed between the sleeve and the clevis by means of a pin 29 and is threaded into a bifurcatedattaching member 31, one of the forks of which is shown broken away. The attaching member 31 of the link 18 serves to attach the link to the lever 13 and the attaching member of the link 19 serves to attach the link 19 to the lever 16. The distances between the manually operated pedal 1'? and the levers 13 and 16 may be adjusted by rotating the rods 28' within their attaching member 31, and when the proper "ad-' justment is attained the rods are locked against rotation by means of the lock nuts 32. I

The lever 16 is provided with a plurality of holes 20 located at different distances from the pivotal point of the lever to which the attaching member of the link 19 may be connected for the purpose of varying the effective lever arm of .the lever 16. If the effective lever arm of the lever 16 is shortened,

the movement of the piston 14 with respect to the piston 11 will be increased for a given movement of the pedal 17, and conversely, a lengthening of the effective lever arm of the lever 16 will devarying the relative amount of movement of the mo pistons 11 and'14 the-rate at which the pressure is built up in the two pressure devices for a given pedal movement may be controlled.

In adjusting the application of the brakes, the rear wheel brakes 7 are adjusted first by properly adjusting the length of the link 19. When the rear wheel brakes have been adjusted; the front wheel brakes 6 areadjusted in such a manner that the application of the front wheel brakes will take effect slightly after the application of 9 the rear wheel brakes. To accomplish this result, front and rear wheel brake linings will be some-' the linklB is made long enough to retard the apwhat different and the compensating devices 23 plication of the front wheel brakes, since the in the rods 18 and 19 will prevent an excessive longer the link the more the application of the braldng effect occurring on one set of ,wheels in sbrake will be retarded. the event the brakes on the other set of wheels 80 As the' lever-'17 is depressed to apply the brakes, either wear more rapidly or are improperly adthe links'18 and 19. at first 'as substantially rigid justed after wear." If either of the compensatconnectors actuate the pivoted levers 13 and 16, ing devices moves oif its normal position the respectively, to move the pistons 11 and 14 within operator will immediately be aware of this movethe cylinders 12 and in a pressure producing ment from theslight shockor hammer effect felt direction. The initial-movement of the pistons through the foot pedal when'the' compensating is an idling movement until such time as the inlet mechanism returns to its normal position. when ports 11' and 14' of the cylindersare closed by, the pedal 17 is operated 'with sufllcient force to for example, the pistons 11 and 14,-respectively, compress the spring 26, the nuts 27 are pulled 15 and thereafter the movement is a pressure proaway from the end of the clevis 23. -As soon as,

ducing movement. the operator relieves part or all of the pressure on The adjustable connections between the rods the pedal 17, the compressed spring 26 will ex.- 28 and the attaching members 31, and the adpand; thereby pulling the nuts 2'1 into contact iustments permitted by the holes 20 and 20' enwith the end of the clevis 23 and causing a slight zo'able me to vary or to adjustthe sequence of operahammer effect which can be felt or which is tion of the brake mechanisms in that they may be perceptible by the operator. This will serve as an employed to vary or to adjust the piston positions indicator to the operator that one' set of brakes is ,at which maximum braking pressures are applied, adjusted more closely than the other and should or in other words the lengths of the pressure probe readjusted. 1

25' ducing strokes or movements and hence the It will be seen, therefore, that the link mechlengths of piston strokes or movements; and the anisms 18 and 19 may be adjusted to control the times required for the idling and pressure producsequence of pressures in the separate pressure ing movements as well as the relative speeds of systems and at the same time control the pressures the pistons independently of each other. and prevent them from exceeding a certain 30 After this idling, one of the pistons, for example chosen limit. When the links 18 and 19 are 5 the piston 14 first,'and thereafter the piston 11, placed in the upper holes provided in the levers causes the rear wheel brakes and then the front 13 and 16, the links 18 and 19 are located farther wheel brakes, respectively, to move to a braking from the pivot points of the levers 13 and 16. A position. A further movement of the lever 16 given movement of the foot pedal 1'7, therefore,

5 under the force applied at the lever 17 would tend produces less rotation of the levers l3 and 16 to build up rapidly a-very high pressure in the about their respective axes and consequently pressure device 9 before the pressure in the 'pre'sshorter strokes of the pistons 11 and 14 than will sure device 8 has attained its maximum value. he produced when the springs 18 and 19 are con- This rapid building up of pressure in the pressure nected at lower apertures of the levers l3 and 16.

4o device 9 would tend to retard the depression of In the latter case the links are closer to the pivot n5 thelever 17, and therefore to retardthe building points of the levers 13 and 16 and the same moveup of the desirable pressure in the device 8. d ment of the foot pedal 17 produces greater rota- The spring 26 is, however, of such capacity as tion of the'levers 13 and 16 and thereafter correto retard the rapid increase of pressure in the spondingly'greater movement of the pistons 11 45 pressure device 9 before the pressure therein and 14. The rate of pressure increase in the pres- 2 reaches a maximum and while the pressure in suresystems for a given pedal movement may be the pressure device 8 is approaching a maximum controlled by adjusting length of the lever arm value. By means of a spring 26 with the proper of the levers to which the link mechanisms are characteristics, as soon as the pressure in the connectedn 5o device 9 exceeds a certain value corresponding to yThe apparatus has been described and illusthe tension of the spring, this spring will be flexed trated in-connection with separate pressure sys- I to prevent the rapid building up of pressure in tems for brake mechanisms of motor vehicles. It

' the device 9 and to allow 'afurther'pressure to be will readily be seen that the invention has many built up in the pressure device 8. Since the pres-. other applications and many modifications may be i '55 sure in this device 8 will not have'reached' its made without departing from the spirit and scope 13 maximum value at the time when the pressure in of the invention, which is to'be limited only by the the device 9 reaches its maximum value, a'further appended claims. depression of the pedal 17 results the pressure I claim:

in the device 8 reaching its maximum value, after 1. In a fluid operated brake system for a vehicle so which a further force applied at the pedal causes having two front and two rear wheels, fluid pres- 5 V thesprings in both links 18 and 19 to be flexed sure operated brake mechanisms associated with to prevent the pressure from exceeding safe limits each of said wheels, a master cylinder connected before the pedal reaches the end of its stroke. with the brake mechanism associated with said.

Although in the preferred embodiment of this two rear wheels, a second master cylinder con- 5 invention the brakes upon the rear wheels are nected with the brake mechanism associated with applied with slightly greater pressure at any said two front wheels, pistons reciprocable in pedal position than the brakes upon the front said mastercylinders and capableof alimited wheels for that pedal position, it is to be underamount of idle movement therein, a single manustood that this is not an essential feature of the ally operated element for reciprocating said pis- '10 invention as there may be instances, for example, tons, yieldable means connected to said manuwith trucks more heavily loaded at the forward ally operated element for limiting the pressures end than at the rear, where the pressure should created in said cylinders, and adjustable means be applied with greater force upon the forward between the last said means and said pistons for brakes than upon the rear. No matter how the providing a predetermined sequence of effective 75 brakes may be adjusted initially, the wear on the v operations of said pistons. I V

' ea ers I 2. In a fluid operated brake system, a plurality of fluid pressure operated brake mechanisms, a plurality of master cylinders for operating said brake mechanisms; pistons in said master'cylinders, said pistons being capable of idling therein, a single element for operating said pistons, and adjustable means connecting said. element with said piston for varying the idling speeds of said pistons to vary the sequence of operation of said brake mechanisms.

3. In a fluid operated brake system, a plurality of fluid pressure operated brake mechanisms, a plurality of master cylinders for operating said brake mechanisms, pistons in said master cylinders, said pistons being capable of idling therein, a single element for operating said pistons, and adjustable means connecting said pistons with said element for varying the time of idling of each said piston and thereby the sequence of operation of said brake mechanisms, said means including means for limiting the pressures pro-. duced in said cylinders.

a. In a fluid operated brake system having a plurality-of fluid pressureoperated brake mechanisms and a plurality of operating devices capable of idling and pressure producing movements, associated actuated devices for said operating devices comprising adjustable means for independently varying the operating speeds of said operating devices whereby to vary the sequence of operation of said brake mechanisms,

and yieldable means for retarding the pressureproducing movements and for limiting the maximum operating pressures of said brake mecha-'. nisms.

5. In a fluid operated brake system, a plurality of fluid pressure operated brake mechanisms, a plurality of master cylinders having pistons therein for operating said brake mechanisms, s'aid pistons being capable of idle movement in said cylinders, and adjustable piston operating means for varying the piston speeds during, such idle movements whereby to vary the operation sequence of said brake mechanisms.

6. In a fluid operated brake system, a plurality of fluid pressure operated brake mechanisma'a plurality of master cylinders having pistons therein for operating said brake mechanisms, said pistons being capable of idling and pressure producing movements in said cylinders, a single element for operating said pistons, a clevis operatively connected to each said piston, and a spring in each said clevis, connecting said single element to each said piston, each said spring being of sumcient rigidity as to provide a substantially rigid connection during the idling movements of said pistons but being yieldable at a predeter- 'minedpremure whereby to retard the pressure producing movements of said pistons.

7. In a fluid operated brake system, a fluid pressure operated brake mechanism, a master cylinder having a piston therein for operating said brake mechanism, said piston being capable of idling and of building up the fluid pressure to the braking pressure of said .brake mechanism, 1

means for operating said piston in said cylinder,

piston.

' ERBER'I' C. BOWEN; 1, 

